The present invention generally relates to monitoring tires on a wheeled vehicle, and more particularly to a tire monitoring system and method that senses characteristics of the tread portion of a tire to monitor tire performance.
Wheeled vehicles commonly employ pneumatic tires each mounted on a wheel for contacting the surface of the underlying road. In order to optimize vehicle performance and minimize tire wear and tear, it is important to maintain certain tire characteristics such as the proper tire inflation and tire/wheel-to-road camber to achieve a desired tire-to-road surface interface in order to optimize vehicle grip to the road surface. Tire over-inflation and under-inflation can lead to uneven tread wear, lessened grip at the tire-to-road interface, and reduced tire performance, amongst other problems. The handling characteristics of a wheeled vehicle are directly attributable to the amount of grip, both lateral and longitudinal, obtained by the tire-to-road interface. Thus, it is desirable to optimize tire performance by adjusting vehicle parameters including tire pressure, camber, aerodynamic down force, and other parameters.
To optimize tire performance, it is desirable to monitor the tire-to-road interface. In the past, indirect monitoring techniques have been employed to measure tire contact with the road surface. One technique measures temperature of the tire and uses time-weighted temperature measurements. However, non-uniform airflow around the tires may cause skewed results from uneven cooling. Another technique for monitoring tire contact employs wear measurements, such as measuring a circumferential length of the tire. However, conventional wear measurement techniques generally require extended running to obtain measurement results, and often require trial-and-error methods of tuning.
Another example of a tire monitoring system for sensing the tire-to-road interface is disclosed in U.S. Pat. No. 5,749,984, the disclosure of which is hereby incorporated by reference. The aforementioned patent discloses the use of a single contact sensor located within the tire for monitoring the center tread contact patch length of the tire as the tire contacts the underlying road surface. According to this prior approach, the center tread contact patch length is processed to determine under-inflation and over-inflation of the tire, as well as tire revolutions and speed. While the aforementioned approach provides some degree of accuracy of the tire inflation, a number of drawbacks exist. First, this prior approach assumes that the tire/wheel camber is zero degrees, and thus assumes that the tire is perfectly straight such that the tread portion is parallel to the ground surface. Secondly, the use of a central contact patch length alone provides only a limited degree of accuracy. Third, the amount of information obtained by the single center contact patch length is limited and, thus, does not allow for optimization of other vehicle driving characteristics.
Accordingly, it is therefore desirable to provide for an enhanced vehicle tire monitoring system that monitors the contact surface area between the tire and the underlying road surface. More particularly, it is desirable to provide for such a tire monitoring system that provides enhanced optimization characteristics to overcome the above-mentioned drawbacks of the prior art tire monitoring approaches.
The present invention improves the tire monitoring on a vehicle by providing enhanced information about the contact patch interface area between the tire and the underlying road surface. To achieve this and other advantages, and in accordance with the purpose of the invention as embodied and described herein, the present invention provides for a vehicle tire monitoring system comprising multiple sensors including a first sensor located on a tire and generating a first electrical signal containing information about a first tread contact length and a second sensor located on the tire for generating a second electrical signal containing information about a second tread contact length. The system includes a controller for processing the first and second electrical signals and determining a first tread contact length associated with the first electrical signal and a second tread contact length associated with the second electrical signal. The controller processes the first and second tread contact lengths to determine a characteristic of the monitored tire.